Examples of electronic components using a ceramic material include capacitors, inductors, piezoelectric elements, varistors, thermistors, and the like.
Among ceramic electronic components, multilayer ceramic capacitors (MLCC) may be used in various electronic devices, due to advantages such as compact size, high capacitance, ease of mounting, and the like.
For example, a multilayer ceramic capacitor may be used in a chip type condenser mounted on a printed circuit board of several electronic products such as imaging devices, for example, liquid crystal displays (LCDs) or plasma display panels (PDPs), computers, personal digital assistants (PDAs), and mobile phones, to serve to charge or discharge electricity therein or therefrom.
The multilayer ceramic capacitor may have a structure in which a plurality of dielectric layers and internal electrodes disposed between the dielectric layers and having different polarities are alternately stacked.
Since the dielectric layers may be composed of a piezoelectric material, when a direct current (DC) or alternate current (AC) voltage is applied to the multilayer ceramic capacitor, a piezoelectric phenomenon may be generated between the internal electrodes, causing periodic vibrations when the volume of the ceramic body is expanded and contracted according to a frequency.
The vibrations may be transferred to a printed circuit board through an external electrode of the multilayer ceramic capacitor and a soldering material connecting the external electrode to the printed circuit board, and thus, the entire printed circuit board may become an acoustic reflective surface to generate the vibrated sound, which is observed as noise. This vibrated sound may have a frequency corresponding to an audio frequency in a region of 20 to 20, 000 Hz, which may cause listener discomfort and is referred to as acoustic noise.
Furthermore, in recent electronic devices, since an attempt to reduce the noise of equipment components has been ongoing, acoustic noise generated in the multilayer ceramic capacitor as described above may become more prominent.
In a case in which the operating environments of equipment are silent, the user regards acoustic noise as an abnormal sound, and thus may interpret the disorder of acoustic noises as the breakdown of equipment. In addition, in devices having a voice circuit, acoustic noise may overlap with audio output, thereby leading to deterioration in the quality of the device.